Method for producing light coloured polyalkylene glycol diethyl ether of fatty acid alcanolamine

ABSTRACT

The invention relates to the production of light-colored polyalkylene glycol diethyl ethers of fatty acid alkanolamines by adding ethylene to the fatty acid alkanolamide in the presence of an alkaline catalyst. The inventive method cossets of alkoxylating in the presence of reducing agents and treating the obtained product by steam in an alkaline medium.

FIELD OF THE INVENTION

This invention relates generally to nonionic surface-active compoundsand, more particularly, to a process for the production of specialcompounds with improved color quality and a reduced percentage contentof secondary products.

PRIOR ART

The production of alkoxylation products of fatty acid akanolamides hasbeen known for some time and is described in detail, for example, in theoverview article by Grossmann [Fette, Seifen, Anstrichmittel, 74(1), 58(1972)]. The reaction of the alkanolamides, preferablymono-alkanolamides, with ethylene or propylene oxide is carried out inthe presence of alkaline catalysts, such as tertiary amines for example[cf. EP 0557462 B1 (Berol Nobel)]. However, the disadvantage is that thereaction products are generally very discoloured and occasionally havehigh contents of unwanted secondary products, more particularly dioxane.Both factors limit the use of the products, more particularly forcosmetic applications.

Accordingly, the problem addressed by the present invention was toprovide an improved process for the alkoxylation of fatty acidalkanolamides which would reliably avoid the disadvantages mentionedabove. More particularly the products would have high color quality anda low content of unwanted secondary products, particularly dioxane.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for the production oflight-colored fatty acid alkanolamide polyalkylene glycol ethers byaddition of alkylene oxides onto fatty acid alkanolamides in thepresence of alkaline catalysts, characterized in that the alkoxylationis carried out in the presence of reducing agents and the reactionproducts obtained in this way are subjected to a treatment with steamunder alkaline conditions.

It has surprisingly been found that the combination of an alkoxylationin the presence of reducing agents with an after treatment with steamunder alkaline conditions gives alkoxylated fatty acid alkanolamideswhich are both particularly light-colored and also low in unwantedsecondary products. More particularly, the need for a steam treatment athigh pH values was unexpected because steam treatments ofwater-containing surfactants are normally carried out in the neutralrange. In contrast to this experience, it was found that the steamtreatment at pH 6 to 7 results in a significant deterioration in color.

Fatty Acid Alkanolamides

Basically, the choice of the fatty acid alkanolamides used, which arecondensation products of technical fatty acids with mono- ordialkanolamines, is not critical. The educts used are typically fattyacid alkanolamides which correspond to formula (I):

where R¹CO is a linear or branched, saturated or unsaturated acyl groupcontaining 6 to 22 carbon atoms and 0 or 1 to 3 double bonds, R² is ahydroxyalkyl group containing 2 to 4 carbon atoms and R³ is hydrogen orhas the same meaning as R². Typical examples are the condensationproducts of caproic acid, caprylic acid, capric acid, lauric acid,myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid,linoleic acid, linolenic acid, petroselic acid, elaeostearic acid,12-hydroxystearic acid, ricinoleic acid, gadoleic acid, arachidonicacid, behenic acid, erucic acid and technical mixtures thereof, moreparticularly coconut oil fatty acid, palm kernel oil fatty acid, palmoil fatty acid and tallow fatty acid, with monoethanolamine,diethanolamine, monopropanolamine and dipropanolamine and mixturesthereof. Condensation products of coconut oil or tallow fatty acids withmonoethanolamine are preferably used.Alkylene Oxides

Suitable alkylene oxides are ethylene oxide, propylene oxide, butyleneoxide or mixtures thereof. The addition may be carried out in blocks orin randomized form. The fatty acid alkanolamides and the alkylene oxidesare normally used in a molar ratio of 1:1 to 1:25 and preferably 1:2 to1:10.

Alkaline Catalysts

Besides alkali metal hydroxides and carbonates, suitable alkalinecatalysts are, above all, alcoholates, more particularly sodiummethylate, sodium ethylate or potassium tertbutylate. As mentioned atthe beginning, tertiary amines may also be used for this purpose. Thealkaline catalysts are used in quantities of typically 0.1 to 5% byweight and preferably 0.5 to 2% by weight, based on the startingmaterials.

Reducing Agents

Suitable reducing agents are any of the substances known by this name,for example borohydrides, more particularly sodium borohydride, andhypophosphorous acid or alkali metal salts thereof. The quantity used isgenerally from 0.1 to 2.5% by weight and preferably from 0.2 to 1% byweight, based on the starting materials.

Alkoxylation

The alkoxylation of the fatty acid alkanolamides may be carried out inknown manner. Stirred autoclaves are generally used, being freed fromadhering traces of water and atmospheric oxygen by alternate heating,evacuation and purging with nitrogen. The amides are introduced into theautoclave together with the catalyst and the reducing agent and heatedto a temperature of preferably 80 to 150° C. and more preferably 110 to140° C. The alkylene oxide is introduced in portions under a pressure of1 to 10 and preferably 3 to 6 bar. It is advisable to follow theaddition with an after-reaction time lasting one to two hours duringwhich the temperature level can be gradually reduced. After thealkoxylation, the reaction products typically have a Gardner color valueof 3 to 4.

Treatment with Steam

After cooling and expansion of the reaction mixture, the crude reactionproducts are subjected to a treatment with steam for which it isessential to establish an alkaline pH, preferably in the range from 9 to12, beforehand. This is done, for example, by adding an aqueous alkalibase. Steam is then passed through the mixture with continuous stirringat 100 to 120° C. until about 10 to 25% by weight of the steam usedaccumulates as condensate. This typically corresponds to a treatmenttime of ca. 60 mins. The alkoxylation product, which now has a Gardnercolor value of typically below 2 and a dioxane content of less than 1ppm, is then dried.

EXAMPLES Example 1 Preparation of Coconut Fatty AcidMonoethanolamide+4EO

2,929.3 g (corresponding to 11.75 mol) of a C₈₋₁₈ coconut oil fatty acidmonoethanolamide were introduced into a 5-liter stirred autoclavetogether with 25 g (corresponding to 0.85% by weight, based on thestarting compound) of a 30% by weight methanolic solution of sodiummethylate and 5.0 g of a 50% by weight aqueous solution ofhypophosphoric acid (corresponding to 0.17% by weight, based on thestarting compound). The autoclave was evacuated for 30 mins. at 80° C.and then purged with nitrogen. The mixture was then heated to 110° C.and 2,068.0 g (corresponding to 47 mol) ethylene oxide were introducedin portions under a pressure of up to 5 bar. The reaction time was 90minutes. The reaction mixture was then stirred for 60 mins. at 110° C.and then for 30 mins. at 80° C. After cooling and expansion, theethoxylated fatty acid monoethanolamide was obtained as a clear liquid(Gardner color value 3.5; hydroxyl value 168).

Comparison Example C1 Preparation of Coconut Oil Fatty AcidMonoethanolamide+4EO

Example 1 was repeated but without the hypophosphoric acid. Theresulting ethoxylated fatty acid monoethanolamide had a Gardner colorvalue of 3.9 and a hydroxyl value of 164.

Example 2 Steam Treatment of Coconut Oil Fatty Acid Monoethanolamide+4EO

1,000 g of the coconut oil fatty acid monoethanolamide+4EO prepared inaccordance with Example 1 were adjusted to a pH of ca. 11 with aqueoussodium hydroxide solution and introduced into a 5-liter stirred reactor.Steam was passed through the ethoxylate while stirring at 120° C. until20% by weight of water, based on the starting material, had condensed(which took 60 mins.). The product was then dried at 120° C./30 mbar.The end product had a Gardner color value of 1.1 and a dioxane contentof less than 1 ppm.

Example C2 Steam Treatment of Coconut Oil Fatty AcidMonoethanolamide+4EO

1,000 g of the coconut oil fatty acid monoethanolamide+4EO prepared inaccordance with Example 1 were adjusted to a neutral pH of 6.5 andintroduced into a 5-liter stirred reactor. Steam was passed through theethoxylate while stirring at 120° C. until 20% by weight of water, basedon the starting material, had condensed (which took 60 mins.). Theproduct was then dried at 120° C./30 mbar. The end product had a Gardnercolor value of 6.5 and a dioxane content of less than 1 ppm.

1-10. (canceled)
 11. A process for the production of a light-coloredfatty acid alkanolamide polyalkylene glycol ether by addition of analkylene oxide onto a fatty acid alkanolamide in the presence of analkaline catalyst, said process further comprising (a) carrying out theaddition of alkylene oxide in the presence of a reducing agent and (b)treating the reaction product obtained in this way with steam underalkaline conditions.
 12. A process according to claim 11, wherein thefatty acid alkanolamide has the formula (I):

where R¹CO is a linear or branched, saturated or unsaturated acyl groupcontaining 6 to 22 carbon atoms and 0 or 1 to 3 double bonds, R² is ahydroxyalkyl group containing 2 to 4 carbon atoms and R³ is hydrogen orhas the same meaning as R².
 13. A process according to claim 11, whereinthe fatty acid alkanolamide is selected from a condensation product ofcaproic acid, caprylic acid, capric acid, lauric acid, myristic acid,palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid,linolenic acid, petroselic acid, elaeostearic acid, 12-hydroxystearicacid, ricinoleic acid, gadoleic acid, arachidonic acid, behenic acid,erucic acid, and technical mixtures thereof, with monoethanolamine,diethanolamine, monopropanolamine and dipropanolamine and mixturesthereof.
 14. A process according to claim 11, wherein the fatty acidalkanolamide is selected from a condensation product of coconut oilfatty acid, palm kernel oil fatty acid, palm oil fatty acid and tallowfatty acid with monoethanolamine, diethanolamine, monopropanolamine anddipropanolamine and mixtures thereof.
 15. A process according to claim11, wherein the fatty acid alkanolamide is selected from a condensationproduct of coconut oil or tallow fatty acid with monoethanolamine.
 16. Aprocess according to claim 11, wherein the alkylene oxide is selectedfrom a group consisting of ethylene oxide, propylene oxide, butyleneoxide and mixtures thereof.
 17. A process according to claim 11, whereinthe fatty acid alkanolamide and the alkylene oxide are used in a molarratio of 1:1 to 1:25.
 18. A process according to claim 11, wherein thealkaline catalyst is used in an amount of 0.1 to 5% by weight, based onthe starting materials.
 19. A process according to claim 11, wherein thereducing agent is selected from a group consisting of sodiumborohydride, hypophosphorous acid and alkali metal salts thereof.
 20. Aprocess according to claim 11, wherein the reducing agent is used in anamount of 0.1 to 2.5% by weight, based on the starting materials.
 21. Aprocess according to claim 11, wherein the addition of alkylene oxide iscarried out at temperatures of 80 to 150° C. and a pressure of 1 to 10bar.
 22. A process according to claim 11, wherein the treatment withsteam is carried out at a pH value of 9 to
 12. 23. A process for theproduction of a light-colored fatty acid alkanolamide polyalkyleneglycol ether by addition of an alkylene oxide onto a fatty acidalkanolamide in the presence of alkaline catalysts, wherein the fattyacid alkanolamide is selected from the condensation products of coconutoil fatty acid, palm kernel oil fatty acid, palm oil fatty acid andtallow fatty acid with monoethanolamine, diethanolamine,monopropanolamine and dipropanolamine and mixtures thereof, said processfurther comprising (a) carrying out the addition of alkylene oxides inthe presence of reducing agents and (b) treating the reaction productsobtained in this way with steam under alkaline condition.
 24. A processaccording to claim 23, wherein the fatty acid alkanolamide is selectedfrom the condensation products of coconut oil or tallow fatty acids withmonoethanolamine.
 25. A process according to claim 23, wherein thealkylene oxide is selected from a group consisting of ethylene oxide,propylene oxide, butylene oxide and mixtures thereof.
 26. A processaccording to claim 23, wherein the fatty acid alkanolamide and thealkylene oxide are used in a molar ratio of 1:1 to 1:25.
 27. A processaccording to claim 23, wherein the alkaline catalyst is used in anamount of 0.1 to 5% by weight, based on the starting materials.
 28. Aprocess according to claim 23, wherein the reducing agent is selectedfrom a group consisting of sodium borohydride, hypophosphorous acid oralkali metal salts thereof.
 29. A process according to claim 23, whereinthe reducing agent is used in amount of 0.1 to 2.5% by weight, based onthe starting materials.
 30. A process according to claim 23, wherein thetreatment with steam is carried out at a pH value of 9 to 12.